Aftershocks: so far there have been no aftershocks recorded. Some may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.

Historical seismicity: since our records began in 1932 we’ve had 2 events of M4 or greater within 10km of today’s event, the largest was M4.5 (1938/08/18) and the most recent was M4.1 on 09 Nov 1942.

Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed. The closest station shown to the event is CI.WWC at approximately 100km, and the furthest is CI.MLAC at more than 400km.

Aftershocks: so far there have been no aftershocks recorded. Some may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.

Historical seismicity: since our records began in 1932 we’ve had 4 events of M4 or greater within 10km of today’s event, the largest was M4.8 (2013/05/29) and the most recent was M4.1 on 17 May 2017.

Aftershocks: so far (07 Dec 2017, 08:00AM PST) there have been 76 aftershocks recorded for the M4.0 event, the largest M3.6 (smallest M0.6). More may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.

Cumulative event number against time (top) and magnitude against time (bottom) for the events near Julian on 6-7 December 2017. In the lower plot, red stars mark the four events with magnitude three or above.

There were 3 events during the 3 days prior to the earthquake (within a 15 km radius), the largest was M2.6 (2017/12/07).

Historical seismicity: since our records began in 1932 we’ve had 9 events of M4 or greater within 10km of today’s event, the largest was M4.7 (1957/01/24) and the most recent was M4.5 on 10 Oct 1984.

Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed. The closest station shown to the event is CI.DGR at approximately 75km, and the furthest is CI.MLAC at more than 500km.

Below is a playlist of the waveform data associated with this sequence, as recorded in our Live Seismograms Feed. The closest station shown to the event is CI.DGR at approximately 75km, and the furthest is CI.MLAC at more than 500km. More videos may be added as new events occur.

Aftershocks: so far (09 Nov 2017, 05:53PM PST) there have been 5 aftershocks recorded, the largest M1.5 (smallest M0.8). More may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.

There were 29 events during the 3 days prior to the earthquake (within a 15 km radius), the largest was M3.1 (2017/11/09).

Historical seismicity: since our records began in 1932 we’ve had 34 events of M4 or greater with in 10km of today’s event, the largest was M5.6 (2005/06/12) and the most recent was M5.2 on 10 Jun 2016.

Aftershocks: so far (26 Oct 2017, 02:52PM PDT) there have been 2 aftershocks recorded, the largest M2.1 (smallest M1.5). More may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.

Historical seismicity: since our records began in 1932 we’ve had 4 events of M4 or greater within 10km of today’s event, the largest was M4.7 (1959/10/01) and the most recent was M4.0 on 09 Jan 1989.

Aftershocks: so far (17 May 2017, 08:29AM PDT) there have been 6 aftershocks recorded, the largest M3.0 (smallest M1.8). More may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.

Historical seismicity: since our records began in 1932 we’ve had 3 events of M4 or greater within 10km of today’s event, the largest was M4.8 (2013/05/29) and the most recent was M4.8 on 29 May 2013.

Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed. The closest station shown here is CI.SYP, approximately 12 km from the epicenter, and CI.LCP, approximately 43 km from the epicenter.

Aftershocks: so far there have been no aftershocks recorded. Some may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%%) that a larger quake could occur, with the likelihood decreasing over time.

Historical seismicity: since our records began in 1932 we’ve had 42 events of M4 or greater within 10km of today’s event, the largest was M6.6 (1968/04/09) and the most recent was M4.3 on 09 Feb 2007.

Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed. The closest station shown here is CI.RXH, approximately 40 km from the epicenter, while the furthest stations (e.g. CI.VOG, CI.PHL) are over 450 km from the epicenter (no clear earthquake signal recorded).

Aftershocks: so far (14 Mar 2017, 08:25AM PDT) there have been 2 aftershocks recorded, the largest M0.9 (smallest M0.9). More may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.

There was 1 event during the 3 days prior to the earthquake (within a 15 km radius), with M0.9 (2017/03/12).

Historical seismicity: since our records began in 1932 we’ve had 12 events of M4 or greater within 10km of today’s event, the largest was M4.7 (1936/02/23) and the most recent was M4.1 on 13 Feb 2010.

Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed. The closest station shown here is CI.RVR, approximately 13.5 km from the epicenter, while the furthest stations (e.g. CI.VOG, CI.PHL) are over 300 km from the epicenter.

A seismic swarm commenced on December 31st, 2016, near Brawley. So far there have been more than 250 events recorded.

The largest event in the swarm so far was a M3.9 on 31 Dec 2016 at 15:06:56 PST, (32.975, -115.545), depth 14.5km, 2km WSW of Brawley, California

8 events over M3 have been recorded and more than 80 events over M2. More than 250 events over M0.5 have been recorded.

Cumulative number of events over time (top) and event magnitudes over time (bottom) for the swarm near Brawley.

Map showing events in the swarm near Brawley coloured by time (blue early, red late) and sized by magnitude. The star marks the largest (M3.9) event in the cluster. Faults are shown as grey lines. Historical seismicity above M4.5 is marked by grey stars and magnitude values.

Historical seismicity: since our records began in 1932 we’ve had 22 events of M4 or greater within 10km of today’s event, the largest was M5.8 (1979/10/16) and the most recent was M4.2 on 28 Aug 2012.

This event is the largest so far in a small cluster of events that started at about 2:30am PDT, consisting of about 35 recorded events. A few events were also recorded in the same area on 26 Oct 2016. A smaller cluster of events also occurred on the 26 Oct 2016 about 3km to the west of the most recent seismicity, giving a total of approximately 50 events over the last 6 days. We have recorded 4 events over M3 and more than 20 events over M2.

Current cumulative event rate and magnitudes for the small swarm near Niland.

The events are in the southern section of the Brawley Seismic Zone, a relatively active area for seismicity. Swarms occur relatively frequently, notably the swarms that occurred during the 1970’s and 1980’s in this area made the zone among the most active areas in all of California.

Historical seismicity: since our records began in 1932 we’ve had 11 events of M4 or greater within 10km of today’s event, the largest was M5.1 (2005/09/02) and the most recent was M4.2 on 24 Dec 2014.

Relocated events for the small swarm near Niland, forming a very tight cluster. Figure provided by Egill Hauksson, Caltech.Catalogue events in the current small swarm near Niland coloured by time (blue early, red late) and sized by magnitude. Historic seismicity above M4.5 is marked by a grey star and the event’s magnitude.

The Brawley Seismic Zone is a north-striking zone of northwest and northeast-striking faults that extends from the southern end of the San Andreas fault to the northern end of the Imperial fault. It is often considered a remnant spreading center in the transition from the Gulf of California mid-ocean ridge to the San Andreas transform fault. Historically, activity includes both northeast-oriented cross-faults that typically involve left-lateral faulting, and activity on northerly to northwesterly-oriented strands (right-lateral faulting) of the zone. The largest events to have occurred on the cross-faults were the Elmore Ranch event in 1987, which is considered to have triggered the Superstition Hills event less than 12 hours later, and the Westmorland event in 1981. The Brawley Seismic Zone is proximal to the southern San Andreas fault, the San Jacinto fault zone, and the Imperial fault.

The pattern of Brawley swarms of the 1970’s was a large number of very small earthquakes (sometimes exceeding 10,000 events) with up to a dozen moderate events of magnitude 4 or so, but no clear mainshock larger than the other events. The 1970’s swarms would be highly active for a few days and then taper off over the next week or two.